This application is a continuation-in-part of application Ser. No. 10/338,764, filed Jan. 7, 2003, now abandoned, which was a continuation of application Ser. No. 09/684,696 filed Oct. 4, 2000, now U.S. Pat. No. 6,502,319.
This invention relates to hand tools, and in particular the invention is concerned with a hand tool for projecting a reference beam of visible light for precise alignment on floors and walls.
For some time laser beams have been used in construction for level references, vertical references and layout on floors and walls. Typically a construction worker marks the floor or walls indicating the location of walls, windows, or other building elements to be constructed. A chalk line is often used to permanently mark the walls or floors. This is a two man job with one man holding one end of the chalked string while the other snaps it, releasing chalk dust which makes the mark.
The most common prior laser device is a simple carpenter's level with level vials and with a laser beam projector attached. See FIG. 1. Many thousands of these are in use today. U.S. patents in this area include Genho U.S. Pat. No. 4,221,483, Rando U.S. Pat. No. 6,009,630 and others. Although indicating level, these levels do a poor job of projecting a beam on a floor or wall. The assignee of this invention has made a product for producing two beams of visible light on the floor for the purpose of laying out a 90° corner, described in U.S. Pat. No. 6,202,312, incorporated herein by reference. This instrument uses a collimated beam of light and an adjustable cylinder lens to convert the round beam into a fan of light and thus project a line on the surface. This is not a very efficient use of the laser diode light because of the natural divergence of the diode and cropping of the beam in collimation. Typically the laser diode beam divergence is 30° in one axis and 8° on the transverse axis. About half the light is lost in the collimation process. In addition, the line can be focused for only one distance. Such an optical system is shown in plan view in FIG. 2 herein and in side view in FIG. 3 herein, and is the present state of the art. Both the problems of efficient use of the laser light and focusing continuously along a line are solved by the current invention.